This invention relates to removing contaminants from a duct, pipe, or the like, and, more particularly, to removing contaminants from a duct, pipe, or the like, using everting membrane assemblies.
The nuclear industry and many other industries that process hazardous materials use special ventilation systems to protect workers from dust and vapors associated with handling and machining the hazardous substances. An important component of ventilation systems is ducting or piping for moving vapors and particles from the workplace to a plenum volume that contains high efficiency particle absorber (HEPA) filters for removing the hazardous materials from the air flow.
These ducts and pipes then collect residual particles that were not carried to the filters. The hazardous particles contaminate the interior of the ducts and pipes and must be periodically removed from the interior of the ducts and pipes, and certainly must be removed when the ducts and pipes are removed from the workplace. One method for removing adherent contaminates is sandblasting interior portions of the ducts or pipes, with a concomitant risk of particulate spread and contamination of workers.
One possible approach to this problem would be to install a liner to contain the contamination between the duct or pipe and the liner. U.S. Pat. No. 4,778,553 to Wood describes a method for lining a pipe with a flexible tubular sleeve, generally for the purpose of rehabilitating older pipes. As taught by Wood, a fibrous liner material is impregnated with a curable synthetic resin and the liner is installed over a carrier tube. The carrier tube is then everted into the pipe to install the liner along the pipe wall. Hot water is introduced within the carrier tube to cure the resin in the liner material to cause the liner to become rigid along the pipe wall. The carrier tube may then be withdrawn from within the liner. It will be understood, however, that the entire pipe must then be treated as a contaminated object for subsequent disposal.
Ventilation systems are frequently complex, with numerous bends and branches. An impregnated fibrous liner would be expected to have an increased resistance for movement along the pipe so that considerable internal pressure may be required to evert the carrier tube within the pipe. Wood teaches the use of a pull through cable, or the like, to attach to the everting carrier tube, whereby a pull on the cable assists the eversion process. But the cable merely drags along the pipe interior and, if contamination is present, either spreads the contamination or becomes contaminated in an unconfined manner.
The present invention is directed to these problems and enables duct and pipe wall contamination to be removed from the duct or pipe in a confined manner. Accordingly, it is an object of the present invention to use everting membrane assemblies to remove contamination from a duct or pipe while confining the contamination within the membrane assembly.
Another object of the present invention is to enable the use of a relatively high pressure membrane for installing an impregnated contaminant-trapping fabric.
One other object of the present invention is to assist in the installation of an impregnated fabric while maintaining confinement of any contamination.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.